Manufacture of artificial materials



March 1937- 1 w l. TAYLOR ET AL 2,072,928

.MANUFACTURE OF ARTIFICIAL MATERIALS Filed Dec. 27, 1933 INVENTORS WNW/m LTriuQor Lesh e. B. G'Uokms AT TORNE Y5 Patented Mar. 9, 1937 UNITED STATES PATENT OFFICE MANUFACTURE OF ARTIFICIAL MATERIALS tion of Delaware Application December 27, 1933, Serial No. 704,116 In Great Britain, January 6, 1933 9 Claims.

This invention relates to the manufacture of artificial materials and particularly to the manufacture of artificial filaments by the dry or evaporative method.

The invention is especially concerned with a process of production of artificial filaments by the dry or evaporative method in which the filaments are stretched in the course of their production for the purpose of improving their quality 10 e. g. by imparting increased fineness and increasing their strength. It is an object of the present invention to provide an improved method for carrying out such a stretching process.

British Patent No. 324,061 describes a method of spinning filaments into a vacuum, or into an evaporative atmosphere at a substantially reduced pressure, whereby great advantages may be obtained, e. g. by reason of economy in the heating of the evaporative zone, and in the recovery of solvent material, and by reason of improved qualities in the filaments produced, especially as regards roundness of cross-section. The present invention is of especial importance in connection with the employment of a vacuum or 25 reduced pressure in the zone in which evaporation of the filaments takes place.

According to the invention, a spinning solution is extruded in the form of filaments into an evaporative zone, and the filaments are led from such zone while still containing a high proportion of solvent material and are subjected to a stretching operation which is applied to that part of the filaments which lies outside the said evaporative zone. In this manner a very considerable 35 amount of stretch may be applied to the filaments, so that filaments of very fine denier are produced whose strength in proportion to their denier is quite considerably increased.

While the invention is of most marked importance when used in connection with the vacuum method of spinning described in British Patent No. 324,061, it may also be employed in spinning operations using substantially atmospheric pressure, i. c. with only a small degreeof suction 45 amounting to a pressure difference of a few inches of water, to draw evaporative medium through the spinning cell. In the present specification the term vacuum is employed to connote substantially reduced sub-atmospheric pressures, ranging 5 from say, inches of mercury upwards, as quite distinct from the slight degree of suction normally employed in dry spinning operations.

The vacuum method described in British Patent No. 324,061 enables, however, the initial 55 evaporation necessary for the purposes of'the present invention to be achieved very rapidly and after a very short run of the filaments in the evaporative medium, so that when evaporation has proceeded to such an extent as to leave the filaments with a content of, say 50% or thereabouts of solvent material they may be led out of the vacuum, e. g. by the means described in U. S. Patent No. 1,949,983, and subjected to the stretching operation. On leaving the evaporative medium and before being stretched the filaments may, if desired, be lubricated by passing over any suitable oil applying device such as a wick or a rod, roller or the like moistened with lubricating material. The application of a lubricant at this point in the process prevents the content of solvent material from rendering the filaments so sticky as to adhere to each other or to the stretching means or to any other object with which they may come in contact.

Stretching is most conveniently effected by means of stretching rollers round which the filaments pass in succession, these rollers being adapted to rotate with different peripheral speeds, so that the filaments between them are stretched. The stretch imparted in this manner is thereby not communicated to the filaments which are about to reach the stretching means. Furthermore, the spinning conditions inside the chamber in which evaporation is taking place need not be disturbed in the manipulation of the stretching means or of the filaments passing round and between them. This is highly desirable in any form of spinning and is of particular importance in connection with vacuum spinning, in which the vacuum must be broken each time the cell is opened.

If the method of spinning the filaments in a vacuum is employed, the arrangement of British Patent No. 324,061 and U. S. Patent No. 2,007,389 may be-used, the threads being removed from thespinning cell described in these specifications by a substantially air-tight auxiliary exit' some distance above the exit usually provided near the bottom of the cell; or the cell may be partitioned to form an upper vacuum zone. and a lower stretching zone, the filaments passing from the one zone to the other through a substantially air-tight exit. On leaving the cell or upper zone, as the case may be, the filaments may be passed over a Wick or like lubricating device, round a roller near the level of the exit, subsequently descending to a second stretching roller. rotated with a higher peripheral speed than the first so as to stretch the filaments, said rollers feeding the filaments to a cap spinning device.

Aspreviously stated, by the methods of the present invention a very considerable degree of stretch may be imparted to the filaments so that very fine filaments of greatly increased strength may be produced. Thus the filaments when submitted 'to the stretching operation may contain say 40-60% or more of the solvent material, and while in this condition may be stretched to any required extent, say 200 or 300% or more of their extruded length. Where the stretching rollers are enclosed, the rate at which the solvent laden air in the vicinity is drawn ofi may be adjusted so as to vary the rate atwhich solvent escapes from the filaments during stretching; If desired, the escape of solvent in this manner may even be inhibited to a greater or less degree by the introduction of solvent vapours into the vicinity of the stretching means simultaneously with the drawing off of air in such neighbourhood for purposes of solvent recovery. Alternatively or in addition to the employment of solvent vapours, liquids may be applied to the filaments for the purpose of augmenting the softening effect of residual solvent therein. Thus, there may be applied to filaments of cellulose acetate by means of a wick or revolving pad, liquids having softening properties, such as suitable mixtures of alcohol/water, alcohol/ethyl acetate, dioxan/water, acetic acid/water, acetone/water, methylene chloride/carbon tetrachloride, ethyl lactate/water, lactic acid/water, methanol/water or diacetone-alcohol/water. In this manner, the softness of the filaments may be maintained and the permissible amount of stretch may be increased.

While the invention is applicable to the production of artificial filaments generally by the evaporative method, it is particularly advantageous in connection with the production of filaments of cellulose acetate or other organic derivatives of cellulose. Examples of other organic derivatives of cellulose are other esters of cellulose such as cellulose formate, propionate or butyrate andthe cellulose others such as ethyl or benzyl cellulose.

While in the above description the filaments have been assumed to follow a generally downward and vertical direction, it is clear that the invention is not limited in this respect. Thus, the filaments may be extruded upwardly or horizontally, and may be caused .to follow any desired path during stretching.

By way of example some forms of apparatus according to the invention will now be described in greater detail with reference to the accompanying drawings in which: 7

Figures 1, 2, and 3 are sectional side elevations of three forms of spinning cell according to the invention.

In Figure l a spinning cell 4 is provided with a pipe 5 for the supply of spinning solution, a filter candle 6 and a spinning jet I, the jet I being mounted on a swivel attachment 8. A door 9 at the upper end of the spinning cell gives access to the spinning jet. Heating pipes I are provided within the cell 4. The filaments I I extruded from the jet 1 proceed through an opening I2 in the upper part of the cell, the opening I2 being of the nature described in U. S. Patent No. 1,949,983, and capable of being closed to a diameter which does not substantially exceed the diameter of the bundle I3 of the filaments II passing through it. The filaments issue from the opening I2 as a bundle I3, which is passed over a wick I4 adapted to apply. a liquid material thereto, and round two rollers I5, I6 disposed vertically upon one another. The wick I4 is preferably of the kind described in U. S. Patent No. 2,032,603, being as far as possible closed to the atmosphere, except for a slit in the cover through which the thread passes. When it is employed for the application of an aqueous liquid the rollers I5 and I6 should preferably be of rustless material.

The rollers I 5, I6 and the wick I4 are contained in a casing I! having doors I8, I9 at the top and bottom respectively to give access to the rollers and the thread I3. The upper roller I5 has a hollow shaft in order that it may be fed with a coolingfiuid. After leaving the lower roller I6 the thread I3 passes out of the casing II by the door I9 and proceeds to a cap spinning device 22 by means of which it is twisted and wound.

On account of the short run between the spinning jet I and the opening I2 the filaments II, while sufficiently set to retain their form, will still contain a high proportion of solvent material. The efiect of solvent material contained in the filaments may be augmented by the application'of further solvent material by means of the wick I4, or alternatively the wick I4 may be. employed to apply a non-solvent liquid such as a lubricant adapted to prevent thefilaments of the'bundle I3 from sticking to one another. The two rollers I5, I 6- round which the thread I3 passes rotate with different peripheral speeds so that the thread I3 is stretched between them to any desired extent while it still contains a high proportion of solvent material. In order to inhibit a too early evaporation of the residual solvent in the thread, a cooling fluid may be passed through the hollow axis of the upper roller 20. Air may be drawn 01f from the casing I! by means of the draw-off pipe 2I and conducted to a recovery plant for the removal of solvent which is extruded from the filaments in the casing II. At the beginning of the operation in order to commence spinning, the filaments may be led down the cell 4 as shown in dotted lines at 23 round a guide 24 and out through an opening 25 similar tothe opening I2.

A vacuum may be maintained within the cell 4 by drawing off the contents of the cell and the vapours evaporated from the filaments by an outlet pipe 26. The construction of the exits I2 and 25 as described in U. S. Patent No. 1,949,983 is such as to prevent any substantial entry of air.

In Figure 2, rollers 30, 3| are disposed inside the cell 4, access being obtained thereto through doors 32 in the back of the cell. Below the spinning jet I is a short tube 33 closed at the bottom by a closure 34 similar to the closures I2 and 25' described in Figure 1. The upper end of the tube 33 is closed by means of a hood 35 similar to that described in U. S. Patent No. 2,007,389. The

vacuum is maintained in the tube 33 by means of a vacuum draw-ofi. pipe 36 leading to the vacuum main 31. Through the outer cell 4 air may be passed, entering. by a pipe 38 and leaving by a draw-01f pipe 39, this air being heated on its way up the cell by means of heating pipes I0 and in turn heating the inner tube 33. A baflie 40 is provided in order to cause the heated air been stretched between them leave the cell 4 by an opening 42 and are passed round a-rol1er43 which leads them to a collecting device of the type described with reference to Figure 1.

Referring to Figure 3, the spinning cell 4 is divided into two parts by means of a partition 35 having an opening 46 similar to the openings I2, 25 described with reference to Figure 1. A vacuum may be maintained in the upper part of the spinning cell 4 by means of a vacuum draw-off pipe 41 leading to a vacuum main. The lower part 49 of the spinning cell 4 contains a plurality of rollers 50 rotating with successively increasing peripheral speeds so as to stretch the filaments. Access is obtained to the rollers 50 by means of a door 5| in the back of the cell. After having passed round the rollers 55 and been stretched thereby, the filaments proceed round a guide 52 in the bottom of the cell to a roller 53 leading them to a collecting device. An inlet pipe 54 and outlet pipe 55 are provided in the cell by means of which solvent vapour may be passed through the lower part 49 in order to maintain the filaments in a sticky condition, or alternatively air alone or containing any desired proportion of solvent vapour may be employed. Heating pipes 56 are provided in the upper part of the spinning cell 4 in order to assist in the initial evaporation of the filaments. Small quantities of air may be admitted when desired by the inlet pipe at 48, such air being drawn off by the pipe 41 described above.

What We claim and desire to secure by Letters Patent is:-

1. Process for the production of artificial filaments by the dry or evaporative method, comprising extruding a spinning solution-in the form of filaments into a vacuum, leading the filaments from,and stretching them outside said vacuum while they still contain a high proportion of solvent material.

2. Process for the production of artificial filaments by the dry or evaporative method, comprising extruding a spinning solution in the form of filaments into a vacuum, leading the filaments out of said vacuum while they still contain a high proportion of solvent material, applying to the filaments a lubricant so as to prevent them from sticking to one another and stretching the filaments outside said vacuum.

3. Process for the production of artificial filaments by the dry or evaporative method, comprising extruding a spinning solution in the form of filaments into a vacuum, leading the filaments from, and stretching them outside said vacuum while they still contain a high proportion of solvent material, and augmenting the effect of such solvent material by applying a softening medium to the filaments as they leave said vacuum.

4. Process for the production of artificial filaments by the dry or evaporative method, comprising extruding a spinning solution in the form of filaments into a vacuum, leading the filaments out of said vacuum while they still contain a high proportion of solvent material, stretching the filaments outside said vacuum continuously with their production, and feeding the zone in which the filaments are stretched with the vapours of a solvent for the substance of the filaments.

5. Process for the production of artificial filaments of cellulose acetate by the dry or evaporative method, said process comprising extruding a solution of cellulose acetate in the form of filaments into a vacuum, leading the filaments from, and stretching them outside said vacuum while they still contain a high proportion of solvent material.

6. Apparatus for the production of artificial filaments, comprising a spinning chamber, means for maintaining a vacuum within said chamber, a spinning jet for the extrusion of artificial filaments into said vacuum, an opening in said chamber at a short distance from said spinning jet for the withdrawal of the artificial filaments said opening being only sufficiently large to allow artificial filaments to pass therethrough without interference, rollers outside said chamber and means for rotating said rollers with different peripheral speeds so as to stretch the filaments passing round them.

7. Apparatus for the production of artificial filaments, comprising a spinning chamber, means for maintaining a vacuum within said chamber, a spinning jet for the extrusion of artificial filaments into said vacuum, an opening in said chamber at a short distance from said spinning jet for the withdrawal of artificial filaments said opening being only sufiiciently large to allow artificial filaments to pass therethrough without interference, rollers outside said chamber, means for rotating said rollers with different peripheral speeds so as to stretch the filaments passing round them, and means for applying a liquid material to the filaments issuing from said vacuum.

8. Apparatus for the production of artificial filaments, comprising a cell, an extrusion chamber within said cell, a spinning jet within said chamber for the production of artificial filaments, means for maintaining a vacuum in said chamber, an opening between said chamber and said cell for the passage of the artificial filaments said opening being only sufiiciently large to allow artificial filaments to pass therethrough without interfe'rence, rollers in said cell round which the artificial filaments are caused to pass, means for rotating said rollers at successively increasing speeds so as to stretch the filaments, and internal heating means adapted to heat said extrusion chamber.

9. Apparatus according to claim 6, comprising means for introducing into the zone of the stretching means vapours of a solvent for the substance of the filaments.

WILLIAM IVAN TAYLOR. LESLIE BRISBANE GIBBINS. 

